Gelcoat and Hull

Removing the Gelcoat

I have decided to put a new barrier coat on the bottom. I first have to remove the old gell coat. I have started this using a grinder with 36 grit sandpaper. I take the gell coat down to paper thin thickness and then sand the remaining with a less aggressive sander, like the Bosch with 60 grit. I have found I can get a very smooth finish without gouging the FRP hull.

Hull Erosion and Pitting

I was asked how my HR Rasmus's 34 year old hull looks under the gellcoat. Below are a few pictures of what I think you could expect from a 34 year old hull that has been neglected.

The pictures above were taken close to the waterline. This is the worst of it.

The pictures above were taken along the centerline at the bottom of the keel. The boat was built in halves and laminated together. There is a groove running the length of the boat along this centerline. It was originally patched with epoxy putty. Over time some of this putty has chipped out and eroded. There is hull erossion along this centerline in places. Above are pictures of the worst areas of this erossion on my boat.

Keel Damage

Below are pictures of the keel damage from an impact. I have cut out the bad laminate and will grind out more to make a tapered edge for the new laminate to grab. The brown stain is diesel fuel stains from deisel leaking thru the cracked tank and hull.

5-13-2010 More gelcoat removal today. Worked about 2 hours grinding. That makes a total of nine hours so far. Started using a belt sander to remove gelcoat along the concave bent above the keel. Seems to be working well with fewer gouges along this tough area.

Is the Hull dry after 2+ years on the hard?

I duct taped some clear plastic to the hull in spots to check for hull moisture. I read that if you don't see any moisture between the hull and plastic after a few days, you can expect to have a dry hull. Well, there was not a trace of moisture after a week. So far it looks like this hull has dried out pretty good.

Hull Repair Schedule

Here is the order I will attack the hull repair.

1. Laminate a patch inside fuel tank to plug the hole I cut.

2. Fill the void between fuel tank and bottom of keel with Marine Tex putty.

3. Laminate the damaged area of the keel and fair.

4. Fill the gouges on bottom of keel with thickned epoxy and fair.

5. Laminate a 1/2 thick new bottom to full length of keel.

6. Laminate a 1/4 inch new bottom to fuel tank and sides.

7. Roll on at least 2 coats of epoxy on hull filling voids as epoxy cures.

8. Apply fairing compound while epoxy is still uncured.

9. Sand hull fair when fairing compound has cured.

10. Roll on 3-6 coats of Interlux Interprotect 2000.

11. Sand any imperfections and let dry, then apply bottom paint.

Hull Work

5/17/2010 I finally decided to strip the gelcoat. I can work about 3 hours before my arm gives out. I am using 24 grit disc on my Festool rotary sander. I can use a high speed 4 inch disc sander with 40 grit to quickly take down the gelcoat on the flat surfaces only. It will gouge the hull on any of the curved surfaces. The Festool is easier to control with its variable speed and works ok on curved areas. I still have to be very careful and move the tool constantly to keep from gouging. The hull is eroded most at the waterline and the turn of the bilge. I am stopping most other boat work until the hull is stripped and the area cleaned of fiberglass powder.

The pictures below show the results of 7 hours of grinding as described above.

The condition of the laminate varies greatly depending on location. The areas in the worst condition were at the waterline and at the concave bend just above the keel. The laminate was in best condition on the flat areas of the keel. Any ideas on why there is a variation? Below are pics of these areas.

Flat surface on keel side


Concave bend above keel

More sanding

Put in another 1.5 hours sanding off the gelcoat. My technique and speed are improving. I have started using my 4 inch high speed grinder with 36 grit. I had previously stated that this is too aggressive to safely remove the gelcoat, but my technique is improving and patience declining. I am able to take most of the gelcoat off with the grinder and will finish up with the Festool variable speed rotary sander. It is much faster with the grinder but you must be VERY careful or you will gouge the hull.

Continue to Remove Gelcoat: Best Sanding Technique So Far

5-19-2010 I put in three more hours of sanding on the gelcoat. My patience continues to wear thin, so I tried another technique that is the best so far. Here it is: I start with a high speed 4 inch grinder with 24 grit 4 inch disc. I make nice, fluid sweeping motion going high to low and let the sander travel about 16 inches before a raise it off the hull. I only let the top third of the disc touch the hull. In other words, the sander is tilted at an angle of about 20 degrees. I start this motion using light pressure but quickly increase the pressure while I observe the results as I go. What I am trying to achieve is a nice uniform groove in the gelcoat that just leaves a paper tissue thin thickness of gelcoat left on the hull. I can actually see the laminate through the gelcoat when I finish this stroke. I repeat this stroke right next to the one I just finished and continue down the hull, always starting high and finishing low. Sometimes I have to go over an area twice to get the right depth. This leaves a grooved hull(but only in the gelcoat if done properly), but I take care of it by changing the grit from 24 to 36. I go back and start removing the rest of the gelcoat by placing the disc flat on the hull and letting the rotation of the disc oscillate the sander head in small circles, just like an orbital sander would do. This takes a bit of practice but works great once you get the hang of it. I have found that this technique done right, leaves very few grooves in the hull and is extremely efficient. If you want less aggressive removal use a 6 inch random orbital sander with 36 grit discs instead of the 4 inch high speed grinder with 36 grit disc for the final gelcoat removal.

5-20-2010 Three More Hours of Sanding

I now have about 19 hours total on gelcoat removal. If I knew at the start what I know now I think that could be cut in half. Below are pics of the progess.

Port side almost finished. The gouges on the topsides is old damage that was patched with bondo. I will repatch with epoxy putty.

This is a picture of the gelcoat after going over with 4 inch 24 grit disc. It is rough and grooved but the laminate is just exposed with little grooving.

This is a picture of hull after going over with 24 grit disc and then using a 6 inch 36 grit disc on my Bosch random orbital sander to finish it out. This leaves a very fair surface.

Starboard side almost complete.

Another port side shot.

Another starboard side shot

Rudder hardware showing the blue/black fairing putty used. It was brittle and cracking in spots so I ground out the bad and will replace with new putty.

Gelcoat Removal: Final Analysis

Ok, I have finished removing the gelcoat. I have tried several different methods using various tools and now I can comment on what worked best in removing the gelcoat. The tools needed are a 4 inch angle grinder (I like the Makita ) with a sanding pad and 24 grit sanding discs and a Bosch 6 inch Random orbit sander model 1250DEVS with 36 grit sanding disc. This Bosch sander has been the most used tool throughout this boat project. This sander has a switch that lets you choose between aggressive sanding and less aggressive sanding. I can't say enough good things about it. You also need a 3M full face mask respirator, a spray painters cotten hood, and some tyvek suits and long sleeve gloves. Start with the grinder with 24 grit paper and take off all but a very thin layer of gelcoat as described above in the 5-19-2010 entry. Then switch to the Bosch sander with a 6 inch 36 grit sanding disc and put it on the aggressive setting. Sand 4 foot area at a time and move the sander continuously. Here is the trick: When the hull was laid they sprayed a thickness of gelcoat on the mold prior to laminating. On my boat, the layer of gelcoat is not consistent in thickness, so if you follow the contour of the gelcoat with your sanding, you will come out with an unfair hull. Let the sander take off what it needs to get a fair hull. This will leave some small blotches of gelcoat on the hull. This will actually help in the long run and is like a thin fairing that you can leave on the hull. I have found that blistered and pourous gelcoat will show up and chip off during the first sanding with the 24 grit. What is left after this first sanding is usually good, well bonded gelcoat. I have found that this produces a very fair hull after sanding. The photo below shows the results after using the above method. Notice the small blotches of gelcoat left on the hull. In some areas even more gelcoat is left on the hull.

Patching Holes and Barrier Coat

Why do I have holes in the hull? Well, I took out some thru hulls and seacocks that I will not replace. I decided on a composting toilet (going greener) and that will not need a thru hull. I also removed 2 old transducers. So, I have started patching holes with fiberglass and epoxy.

I did a small test area concerning the epoxy barrier coat. Pic above shows the work. I rolled on 4 coats of epoxy with no fillers or additives and used a plastic 6 inch wide putty knife to work the epoxy in the pits caused by hydrolysis. I had to keep working the putty knife until the epoxy set enough to not run. I did this on the first 4 coats. I then began adding West System barrier coat additive, which is a grey aluminum powder, and rolled on 3 more coats. I let this set and then faired with system three quickfair, let set, and sanded smooth. I then rolled on one more coat of epoxy and alum. powder.

Pic above shows three holes I patched using fiberglass and epoxy. Sanding will come later.

Getting Ready for Major Fiberglass Work

I set up a fiberglass cutting station next to the boat. I found that a 16 foot by 4 ft. table along with sheet rock squares and single edged razor blades works great for cutting sectins of fiberglass. Pics below.

Cardboard boxes to keep my cut fiberglass


Tools that work well for me: squares, straight edge, scissors, and single edge razor blades.


Resin station

Gelcoat and Hull: First Four Coats of Epoxy and Fairing Putty

I spent the weekend working on the epoxy gelcoat. I rolled on 2 coats of pure epoxy with no additive with a 9 inch foam roller. I put it on way too thick. Lack of patience I guess. I would not recommend using a 9 inch roller. I just couldn't control the thickness with it. I worked with System Three general purpose epoxy, using 5 pumps from their mini pump at a time. That was all I could roll on before it set. I then rolled on 2 more coats and added an aluminum powder from West System. I had many pits in the hull from hydrolysis and the epoxy is virtually useless in an unthickened state in filling them. I was told by a West System guy to use a large putty knife and work the epoxy in the pits as it sets. I tried with some success but it was difficult and many pits remained. I did manage to coat the inside of all the pits with epoxy, just couldn't fill them all. I then used System Three Quickfair and used a 6 inch putty knife to trowel the Quickfair on the entire hull with a thin coat. It was not too difficult to get a pretty smooth surface using only the putty knife. It was, however, very hard on the shoulders. I then faired using long boards and then used an 8 inch orbital sander when my shoulders gave out using the long boards. I then rolled on another coat of epoxy with aluminum added using a 4.5 inch roller. I could control the thickness much better with it and got a much thinner and smoother coat. I am slowing down, using only 3 pumps of the epoxy at a time and putting it on much thinner, which I think is the way to do it right. At this point I have 5 coats on and plan to put an additional 2 or 3 more. Pics below:

Pics above are of 4 coats of epoxy and the faired Quickfair Putty.

Pics above are with a coat of epoxy over the faired hull.

Gelcoat and Hull: Starboard Bottom: Day 3 and 4: Coats 6-9.

I have mostly finished the starboard side of the bottom gelcoat repair. I have put on 9 coats of epoxy. It isn't perfect but it is good enough for me. I lack where the boat stands are located. I will brace the boat from the topsides and remove the boatstands for the port side repair. This will save much time. I am improving my technique as I go and will report on the methods that worked best for me when I am finished.

Gelcoat and Hull: Port Bottom: Day 1 and 2

I rolled on 3 coats of pure epoxy and troweled the epoxy into the pits as best I could. I then used a 10 inch sheetrock knife and spread System Three Quickfair over the uncured epoxy. I did this keeping the application as fair as possible. It went on nice and smooth. The next day was spent sanding the fairing putty. This took about 3 or 4 hours. I used good old elbow grease and a long board with 80 grit sandpaper.

Port side faired bottom.

The darker spots are newly applied putty prior to sanding.

Gelcoat and Hull: Port Bottom: Day 3 and 4

I rolled on 1 coat of pure epoxy over the sanded and faired hull. I then added aluminum powder to the epoxy on the next 3 coats. The next day I applied the last 2 coats of epoxy, the last coat being pure epoxy, to make a total of nine coats. And that is that.

Above: Pictures with 7 coats of epoxy applied.

I finished the application of the epoxy gelcoat. Let me say that again. I FINISHED THE EPOXY GELCOAT!!!!!!!!!!! And it feels GOOD! It took me 8 days to apply. Once the technique was optimized, it went on pretty good. Here is my:

Final Analysis: I used System Three General Purpose Resin with Fast Hardener. I rolled it on using a 9 inch yellow foam roller cover made for epoxy. I was able to apply 7 pumps of epoxy, using System Three's mini pumps, at a time. I poured the mixed epoxy in a plastic roller pan and loaded the foam roller with a fairly thin uniform coat of epoxy. This is important. If you start with an inconistent covering of epoxy on your roller cover before a application, it will be harder to roll out in uniform thickness. For best results, I worked the roller up, down, sideways, on the hull several times and then finished with a nice vertical stroke to get a nice uniform layer of epoxy. I rolled on the 10.5 ounces of epoxy (7 pumps equals 10.5 ounces) and then went over the freshly rolled surface with a foam paint brush. That is important. It gets the bubbles out and you can knock down any irregularities. Day one: The first two coats is pure epoxy. The third coat I added West System aluminum powder. Then I faired the bottom using System Threes Quickfair. That worked really nice and I spread it with a 10 inch sheet rock knife (stainless steel blade). That combination worked perfect for me. Day 2: I sanded with 80 grit using a long board sander. Coats 4 through 7 I added West Systems aluminum powder added for added water barrier properties. The aluminum powder made it significantly harder to work with and if I had it to do over again I might not use it. It thickened the epoxy and was harder to keep smooth. Day 3: Coat 8 I added aluminum powder and coat 9 was pure epoxy. Important notes: It took most of each morning for the condensation to evaporate from the hull before I started, which was at least to 10:30 A.M. and later. Each coat of epoxy would not increase smoothness of the hull, it would actually decrease smoothness. The more coats, the more "sags" were left in the hull. The epoxy actually magnifies irregularities and sags itself. They were acceptable to me, so I did nothing about it except to use the foam brush after application and smooth out what I could. In order to get a really smooth hull, I would think one would do what I have written above, but after the second to last coat, fair the hull again with Quickfair after the epoxy coat is dry enough and put just one more coat of epoxy on the sanded and faired fairing putty after it dries. I believe this would produce a very smooth surface. The reason you couldn't just do one fairing job before the final coat of epoxy is because the 7 coats of epoxy prior would "magnify" the pits in the hull. It would look like the suface of the moon. You must fair the hull early in the process (but it is recommended to apply two coats of epoxy first, regardless) and then do another late in the process to get a really smooth surface. I was able to work one entire side of the bottom at a time. That surprised me. I thought I would work about 1/3 of each side at a time until finished and then go to the next section. No problems working the entire side at a time. Temps were around 75 to 80 degrees throughout this 8 day period. I had 6 plastic roller pans on hand and used one pan for one coating on one side. I would then get a new roller pan and roller cover for the next coat, and so on. This kept the epoxy from getting gooey. After I had used all six pans, I could pop the epoxy off the first pan to get a nice clean pan for the next coat. I had acetone and rags on hand to clean epoxy from my roller frame after each coat. That kept them usable. Lighting is important to see the epoxy as it is applied. It is clear and very hard to see what you have applied at times. System Three says you have a 72 hour window for applying coats of epoxy on top of each other without sanding. I saw no evidence to the contrary. Everything worked very well. This system worked for me and I am very happy with the results.

Hull: Removing the Gelcoat

I removed the gelcoat in one morning using 24 grit sanding disc and grinder and finishing with 36 grit using random orbit sander. The pic above shows the work. I have circled hydrolized laminage to remove with a disc sander and repair.

The above pic shows the level of hydrolysis on the topside laminate? I question this because I don't really know if that what it is. It could also be the 35 year old chaulky gelcoat chipping off the laminate during the sanding. Anyway, the gelcoat in the midsection of boat was so chaulky and loose that I decided the only real solution was revoval.

Pics above show the patches that replaced some hydrolized laminate. Most of the grinding was only 3/16 inch deep. It took 8 layers of 10 oz. fiberglass cloth to fill the voids.

Hull: Topsides Gelcoat Replacement: 4/19/2011

I have previously removed part of the topside gelcoat because it was in such bad shape. Today I mixed three pumps of epoxy at a time and added milled fiberglass. I rolled this on the topsides and then used a 10 inch sheetrock knife to smooth it out and work the epoxy into the pits. After two coats of the epoxy/milled fiberglass mixture, I filled all remaining pits and holes with an epoxy/wood flour mixture. I bladed this on with a 10 inch sheetrock knife and worked it all over and as fair as possible. It looked reasonably fair. I then let this set a bit and then went over the area with System Three Quickfair. Tomorrow I will sand this out and continue to add fairing putty and sand until fair.

Hull: Topsides Gelcoat Replacement, Fairing, and Painting: 5-10-2011

I have been working on and off on the topsides for about a month now. It has turned out to be much more work than I had anticipated. I have the port side looking pretty good now. This is what I have done: 1)I took off a section of bad gelcoat with 36 grit orbital sander on port and starboard sides. 2)I then patched some bad areas with epoxy and glass. 3)Next, I rolled on a coat of epoxy on the exposed fiberglass. 4)Before that cured I rolled on another coat of epoxy thickened with milled glass. 5)I then used a 10 inch sheetrock knife to blade the epoxy into the pits. I repeated steps 4 and 5. 6) I then mixed epoxy and wood flour to peanut butter consistency and used my 10 inch sheetrock blade to apply. 7)Before that cured I applied System Three Quickfair fairing compound over the area and smoothed it out best I could with the sheetrock knife. Steps 3-7 must be done on same day and it took me about 4 hours to do a 2 foot by 12 foot area. Next comes all the tedious work of sanding the fairing compound, reapply, sand, reapply, sand. This involves much more work than I had thought. After I had had enough fairing, I sprayed on Interlux Primekote epoxy primer to the entire topside. Below are some pictures of the work.

System Three Quikfair has been applied over epoxy-milled glass and epoxy-wood four coats to build up the new starboard gelcoat(above).

Port side showing Interlux Primekote layer(above).

Replacing epoxy putty on stearn center line. The Rasmus was built in halves and bonded together and faired at the factory using epoxy putty. This putty will crack and chip over time and needs to be replaced. Below is a picture of new putty on the stearn centerline(above).

Hallberg Rassy Rasmus 35 Rudder Assembly

Below are schematics of the rudder assembly if anyone is interested.

Hull: Topside Fairing 6-20-2011

I have been working for two months on the topside gelcoat application and fairing. It has been much more work than I ever could have imagined. I am thankfully nearing the end of it, no matter how it turns out. So to recap, I have removed the crumbling gelcoat down to the FRP from the midsection of the Rasmus on both sides, removed any damaged FRP and repaired with epoxy and glass, coated with two coats of pure epoxy, then a coat of epoxy thickened with wood flour and milled glass, then system three quickfair, sand, more quickfair, sand, quickfair, sand, etc, etc. You get the picture. Last week I got the fairing to an acceptable level and applied a final coat of pure epoxy to seal. I have let it cure for a week and will now remove amine blush, sand with 80 grit, prime with Interlux Primekote and finish with Interlux Perfection. Below are pics of the starboard side after it had been sealed with pure epoxy. Next comes the Primekote.

Starboard side that is sealed with epoxy and ready for Interlux Primekote.

Transom ready for Primekote.

Starboard side.

Starboard midsection.

Work table next to the Rasmus.

Hull: Keel FRP Repair

I have started the keel repair. The front edge and some of the bottom of the keel has been damaged through the years and there has been FRP degradation and delamination as a result of little to no maintenance. I had to make a decision here, do I grind out all the damage and repair or do I grind the worst of it and not go too deep with the grinder and cap the bottom with another skin of fiberglass. I decided not to grind deeply, who knows where there damage ends. I will fiberglass another skin on top of the bad fiberglass and in effect "cap" it like a tooth cap. I will wrap the knew fiberglass around the bend of the keel bottom and go nine inches up the sides to ensure I have attached the cap to undamaged fiberglass. I will do it in sections and will start with the forward edge of the keel. I have ground around one quarter of an inch of damaged fiberglass off the bottom and front edge of the keel. Pictures below.

You can see the delamination on the left edge of the keel bottom. It looks to me like there has been about 3/8 inch of FRP removed from groundings and grindings. I will build this back up with new fiberglass and wrap it up the sides 9 inches to "cap" the bottom of the keel.

I removed the old epoxy putty from the centerline groove and replaced with Interlux WaterTite Epoxy Putty.

I will "cap" up to the paint line.

I have nearly finished the first phase of the keel repair. I have "capped" the front edge of the keel for four feet. This took three days of layup work with 6 oz. fiberglass and epoxy. Below are pics.

First phase of keel repair complete.

The blue material is Interlux Watertite Epoxy putty used for fairing.

I am applying 9 coats of epoxy to seal the work from water intrusion.



Painting: Topsides

Today I sanded the epoxy clearcoat with 80 grit and applied Interlux Primekote on the transom and starboard sides. It was joyous, having completed all the prep work prior. It went on nice and easy even with the ridiculously steamy weather we have had lately. Below are pics.

Hull: Repairing Damaged Keel Bottom

I have finished the front section of the keel repair and put the weight of the boat on the repair area. It seems to have taken the load with no problems. I have ground the rest of the keel bottom and ground 6 inches up the keel sides with 36 grit sandpaper. That should give the new fiberglass "cap" a rough surface to hold to. I will fill all holes with epoxy/wood flour putty, lay in 18 oz roving fiberglass into the putty, and then lay 20 layers (1/4 inch) of 6 oz fiberglass to make the repair cap. Pics below.

I ground out the worst of the rotten fiberglass and you can see there is still plenty bad fiberglass left. I believe a new fiberglass "cap" is the best way to deal with this problem.

I have ground the keel bottom and sides in order to have a good "tooth" for the "cap".

The new cap at the front edge of the keel. I have put put most of weight of the boat on this new "cap" and it seems to have taken the weight with no problems.

Hull: Keel Repair

I have capped the aft 26 inches of keel bottom with 1/4 inch of new fiberglass. It took 20 layers of 6 oz glass to get the 1/4 inch thickness. I will smooth out edges with grinder and fair later. Pics below.



I will fair the edges later.

Hull: Keel Repair (7-26-2011)

Last week Darryl and I laid down the fiberglass/epoxy "cap" over the bottom of the keel. It takes about 20 layers of 6 oz. glass to make 1/4 inch thick laminate. It was hard work but we had no problems putting it on. I laid on my back doing the laminate work while Darryl mixed epoxy. I would lay a layer on and wet it out real nice, let it sit until it just got tacky so the next fiberglass layer would stick and not slump off, then wet it out, etc. etc. Pics below:

Fiberglass "cap" on bottom of keel above

Before fiberglass "cap" above

After fiberglass "cap" above

Hull/Painting: Topside Painting with Interlux Perfection

Today I sprayed on the first coat of Perfection two part polyurethane paint. It sprayed on really nice except for overheating in my tyvek suit and full face positive pressure respirator. I got so hot I had to stop and get inside to cool off before I could go back out and finish the job. Prior to painting I sanded with 240 grit sandpaper using a festool finish sander with vacuum attachment. I wiped hull clean with Interlux 2333N solvent and then vacuumed the hull. That produced a very clean hull to paint. Humidity was 65% with 94 degree F temps. Below are pics.

8-24-2011 Hull: Fairing Keel and Painting Bootstripe

It was cool here today(72) and was a great day to grind down my keel cap and get it ready for epoxy gelcoat. Also I applied the port side bootstripe. Pics below.

Two coats of Interlux bootstripe one part polyurethane enamel


I faired the keel cap with rotary sander and 36 grit disc. It is ready for fairing compound and epoxy gelcoat.

Front edge of keel repaired with glass/epoxy and ready for fairing and epoxy gelcoat

Hull: Keel Cap Fairing and Epoxy barrier coat 8-29-2011

I first appled 2 coats of System Three epoxy on the surface of the keel cap that I laminated on the bottom of the keel and also on the rudder that I patched and faired. I let that dry to a tacky state and then faired using System Three Quickfair and Interlux Watertite. I let that dry for three hours then sanded smooth. I then applied two more coats of epoxy for a barrier coat. Tomorrow I will apply at least three more coats of epoxy, then sand and paint, baby! That will finish the hull work. Really exciting to get through this long and hard hull work. Pics below:

The cap that I laminated on bottom of keel and 6 inches up the side is 1/4 inch thick(20 layers of 9 oz glass and epoxy). I am happy that is will be barely noticeable after the bottom paint is applied.

Rudder faired and ready to finish out


Starboard side

Boot stripe looking good.

As you can see, the 1/4 inch thick keel cap will be barely noticeable.

Port sid


Hull: Painting Bottom

I applied a coat of Petit Hydrocoat bottom a couple of days ago. It is water based paint and very easy to work with. I will apply another coat and then wait for launching to apply the last coat. I was happy to see all the fiberglass work pretty much disappeared when the paint went on. I am still not completely satisfied with my topside Perfection paint job but will see if I have the time and energy to recoat that later. Pics of bottom paint below.